title: Reinitiation and other unconventional posttermination events during eukaryotic translation.
abstract: During ribosome recycling, posttermination complexes are dissociated by ABCE1 and eRF1 into 60S and tRNA/mRNA-associated 40S subunits, after which tRNA and mRNA are released by eIF1/eIF1A, Ligatin, or MCT-1/DENR. Occasionally, 40S subunits remain associated with mRNA and reinitiate at nearby AUGs. We recapitulated reinitiation using a reconstituted mammalian translation system. The presence of eIF2, eIF3, eIF1, eIF1A, and Met-tRNAi(Met) was sufficient for recycled 40S subunits to remain on mRNA, scan bidirectionally, and reinitiate at upstream and downstream AUGs if mRNA regions flanking the stop codon were unstructured. Imposition of 3' directionality additionally required eIF4F. Strikingly, posttermination ribosomes were not stably anchored on mRNA and migrated bidirectionally to codons cognate to the P site tRNA. Migration depended on the mode of peptide release (puromycin > eRF1⋅eRF3) and nature of tRNA and was enhanced by eEF2. The mobility of posttermination ribosomes suggests that some reinitiation events could involve 80S ribosomes rather than 40S subunits.
authors.affiliation: Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
authors.forename: Maxim A
authors.initials: MA
authors.lastname: Skabkin
authors.forename: Olga V
authors.initials: OV
authors.lastname: Skabkina
authors.forename: Christopher U T
authors.initials: CU
authors.lastname: Hellen
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Pestova
mesh_terms: D000818:Animals; D018388:Codon, Terminator / Q000235:genetics* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D056890:Eukaryota / Q000235:genetics*; D015977:Eukaryotic Initiation Factor-1 / Q000378:metabolism; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism; D039562:Eukaryotic Initiation Factor-4F / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism*; D010442:Peptide Chain Initiation, Translational; D010454:Peptide Termination Factors / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011691:Puromycin / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D012270:Ribosomes / Q000502:physiology*; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D018388:Codon, Terminator; C107465:ERF protein, human; D015977:Eukaryotic Initiation Factor-1; D015852:Eukaryotic Initiation Factor-2; D039621:Eukaryotic Initiation Factor-3; D039562:Eukaryotic Initiation Factor-4F; D046912:Multiprotein Complexes; D010454:Peptide Termination Factors; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; D012097:Repressor Proteins; C026022:eukaryotic peptide initiation factor-1A; C087971:peptide-chain-release factor 3; D011691:Puromycin; D019892:eIF-2 Kinase